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efi/libstub: Buffer output of efi_puts

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Use a buffer to convert the string to UTF-16. This will reduce the
number of firmware calls required to print the string from one per
character to one per string in most cases.

Cast the input char to unsigned char before converting to efi_char16_t
to avoid sign-extension in case there are any non-ASCII characters in
the input.

Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Link: https://lore.kernel.org/r/20200518190716.751506-4-nivedita@alum.mit.edu
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
This commit is contained in:
Arvind Sankar 2020-05-18 15:06:55 -04:00 committed by Ard Biesheuvel
parent cb8c90a08c
commit fd0528a249
1 changed files with 13 additions and 6 deletions
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19
drivers/firmware/efi/libstub/efi-stub-helper.c
View file

@ -8,6 +8,7 @@
*/
#include <linux/efi.h>
#include <linux/kernel.h>
#include <asm/efi.h>
#include "efistub.h"
@ -34,13 +35,19 @@ void efi_char16_puts(efi_char16_t *str)
void efi_puts(const char *str)
{
while (*str) {
efi_char16_t ch[] = { *str++, L'\0' };
efi_char16_t buf[128];
size_t pos = 0, lim = ARRAY_SIZE(buf);
if (ch[0] == L'\n')
efi_char16_puts(L"\r\n");
else
efi_char16_puts(ch);
while (*str) {
if (*str == '\n')
buf[pos++] = L'\r';
/* Cast to unsigned char to avoid sign-extension */
buf[pos++] = (unsigned char)(*str++);
if (*str == '\0' || pos >= lim - 2) {
buf[pos] = L'\0';
efi_char16_puts(buf);
pos = 0;
}
}
}